1. Field of the Invention
The present invention relates to a photoelectric conversion device.
2. Description of the Related Art
In recent years, solar cells which generate electric power without carbon dioxide emissions have been attracting attention from the point of view of global warming prevention. Recently, the Japanese government has started subsidies for solar cells, and moreover, solar cells themselves have come to be less expensive. Thus, solar cells have been in widespread use not only in large-scaled solar power generation facilities but also in standard houses, e.g., on roofs of or outside the houses for power generation.
Therefore, a variety of methods have been suggested in order to increase the amount of electric power to be generated by solar cells. As one of the methods, photoelectric conversion devices have been developed which are achieved by stacking layers for converting incident light into electrical energy (hereinafter, abbreviated as a photoelectric conversion layer). For example, as described in Patent Document 1, a structure is known which is achieved by forming a single crystalline silicon photoelectric conversion layer including a p layer and an n layer as a lower layer and forming an amorphous silicon photoelectric conversion layer including a p layer, an i layer, and an n layer as an upper layer so as to be connected to each other in series.
However, in this stacked structure, incident light first undergoes a photoelectric conversion in the upper photoelectric conversion layer, and then reaches the lower photoelectric conversion layer. For this reason, light loss such as light absorption or reflection by the upper photoelectric conversion layer is caused, and the incident light is thus diminished in the lower photoelectric conversion layer, which results in a decrease in the amount of electric power generated. In addition, there is a need for matching of electric currents produced by the respective photoelectric conversion layers.
Consequently, in order to achieve a large amount of electric power generated from a plurality of photoelectric conversion layers, a photoelectric conversion device using a structure (hereinafter, abbreviated as a light-dividing device) including a layer (hereinafter, abbreviated as a light-dividing layer) which has the function of reflecting light of a specific wavelength and transmitting light of the other wavelengths and a structure (hereinafter, referred to as a photoelectric conversion element) including a photoelectric conversion layer has been suggested as described in Patent Document 2.
In the photoelectric conversion device, incident light is divided by the light-dividing device into a plurality of wavelength bands, and photoelectric conversion elements corresponding to the respective wavelength bands are provided on the optical paths of the reflected, divided light and the transmitted, divided light. Therefore, the light loss can be eliminated which is caused by the stacked structure as described in Patent Document 1. Accordingly, the photoelectric conversion device is capable of generating a large amount of electric power.
On the other hand, photoelectric conversion devices are mainly placed outside, and there is thus a need to expect that pressures due to wind and rain and impacts due to blown-off objects will be applied to the photoelectric conversion devices.